The favorable financial aspects of rearing aquatic life such as fish in a closed system on a commercial scale have attracted investors for many years. The prospective market is enhanced by the fact that oceans and streams are suffering from over-fishing and pollution. The fish industry cannot supply the world demand and the risk of receiving polluted fish is on the rise. Fish raised in closed systems can provide a guaranteed delivery of fish in top condition, at any time of the year, thereby commanding a premium price. Other advantages of closed systems are that they eliminate the problems associated with the discharge of current fish hatcheries. Closed systems eliminate rain/runoff events affecting a hatchery""s water supply, allow absolute control over rearing cycles via temperature control, and allow the ability to treat the fish for disease without the problem of releasing agents into the watershed. Therefore, on paper, raising fish in a closed system shows the potential of a tremendous return on an investment. However, current technology has not produced an economical and fully dependable closed system. Researchers have attempted to create fish culture closed systems for the last 25 years, but none of the systems have been particularly successful commercially and many have simply failed.
The disadvantage of a closed system which makes them unpopular in the fish industry is that closed systems are technically complex. The complexity of the closed system increases the chance of lost fish production due to mechanical failure. Closed system technology can be divided into five major areas: temperature control, maintenance of dissolved oxygen levels, disease control, sediment removal and ammonia removal. For temperature control, current closed systems usually rely on boilers and heat exchangers. Maintaining high dissolved oxygen levels equates to high production levels of fish. Current systems maintain oxygen levels through various aerators and air-injection devices. These devices have proven to be inefficient and subject to failure. Disease control is a must for closed systems, as the intensive conditions provide the potential for disease problems. Normally, the disease problems in flow through systems are treated with various FDA approved antibiotic drugs.
The two major areas which most discourage the use of closed systems are sediment removal and ammonia removal. For sediment removal, many older systems relied on sediment trapping filters that are expensive both to purchase and to operate. Ammonia removal has been the most technologically limiting area for closed-system development. Previous systems have employed various mutations of biofilters. As the name implies, biofilters rely on a biological process of living bacteria converting toxic forms of ammonia to non-toxic forms. The biofilters require several weeks to become established and consume more oxygen than the fish being reared. The biofilters must be removed or isolated from the system should disease treatment become necessary, as the antibiotics used in the disease treatment would simultaneously destroy the biofilter. In addition, bacteria within the filters reduce the pH of the water and increase carbon dioxide levels, each of which must be countered with additives. Far worse, however, is the unpredictable nature of the biofilters to suddenly xe2x80x9cdie-offxe2x80x9d and cease to function. The aqua-culturist has no choice but to watch the fish in the system die of ammonia poisoning. Another form of ammonia removal is the use of zeolite, a naturally occurring mineral. Zeolite has the natural ability to absorb ammonia. Tanks of the mineral can be used effectively to absorb ammonia from fish water. Unfortunately, the zeolite eventually becomes covered and fouled with biological growth, thereby reverting the filters of a closed system to a biological process.
It is an object of the present invention to provide an improved indoor aquatic life rearing system which does not pollute lakes or streams with waste water.
It is an object of the present invention to provide a method of preventing performance degradation of equipment which removes ammonia from water of an aquatic life rearing system.
The present invention provides an aquatic life rearing system which includes at least one rearing tank holding water for rearing aquatic life. Each rearing tank including a first drain. A solid removal means is provided for removing solids from a first drain flow of water that emanates from the first drain. An ammonia removal filter is provided for removing ammonia from said first drain flow. The system includes an ozone input into the first drain flow. The system can further include a gas transfer means for providing oxygen to the first drain flow. The system can also include two drains. Whereby the first drain is a bottom drain at the bottom of each rearing tank and the second drain is a mid-level drain at about the mid-level of each rearing tank. The present invention also provides a method of inputting ozone into the first flow before the first flow enters an ammonia removal filter. The ozone destroys organic matter in the ammonia removal filter and prevents fouling of the ammonia removal filter.